Plate tectonics dated to 3.8 billion years ago

26 March 2007 | Story by Helen Swingler

UCT geologist Professor Maarten de Wit is among an international team that has found evidence that the plate tectonics occurred at least 3.8 billion years ago. Their observations, printed in the latest issue of Science (March 23), indicate that this tectonic activity began before any known structural geological record of Earth.

Evidence comes in the from of the oldest preserved pieces of the Earth's crust in southwestern Greenland, where a rare outcrop in the Isua Supracrustal Belt is found to constitute an ophiolite, dated at 3.8 billion years.

Ophiolites represent ancient 'fossilised' seafloor that formed at oceanic spreading centres that subsequently accreted to a continental plate, surviving unscathed for billions of years.

The finding is significant, pushing back the date of plate tectonic processes, previously thought to be around 2.5 billion years ago, to an era far closer to Earth's conception 4.5 billion years ago.

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